Lester Brown asks for a window seat whenever he flies so that he can look down at the earth. That’s one more vantage point from which to view the evolving environmental panorama he has been examining for almost half a century. He spends a lot of time in the air, heading to audiences in all corners of the planet where his controversial predictions have gained attention.

Over the years Brown, who founded the Worldwatch Institute and the Earth Policy Institute, both in Washington, D.C., has often seemed a gloomy prophet. The subtitles of his most recent worldwide best sellers, the Plan B series, attest to this impression: Rescuing a Planet under Stress, A Civilization in Trouble and, with added urgency, Mobilizing to Save Civilization. He has warned of potentially destabilizing and costly food shortages, populations outstripping dwindling natural resources, water tables falling precipitously and glaciers retreating, bringing drought and floods. Critics have told him to lighten up: humanity has a way of adapting.

Lately, however, Brown has found a new optimism that profoundly moves him, based on the steady growth of alternative energy sources, perhaps most significantly in the U.S. He senses that people at local levels are grasping and acting on the immensity and urgency of climate change, an environmental issue his detractors have said he was late in recognizing. For example, Brown sees more and more communities challenging carbon-emitting coal-fired power plants. He also sees start-up entrepreneurs advancing wind farming and other renewable technologies at a rapid pace, promising even once depressed areas of the U.S. both new sources of income and cheaper electricity.

Many Americans put their hopes in the Obama administration’s political and financial support for new energy sources and in international efforts to confront and attempt to reverse climate change. Although Brown welcomes the new emphasis, he thinks it is too late to pin too many hopes on global pacts, which take years to negotiate and even more years to implement. Most politicians, he says, merely ask themselves what sort of a carbon cut is politically feasible.

Americans are, without much publicity, already moving ahead on their own, changing the face of energy production and consumption, community by community, Brown said in a recent interview in his office at the Earth Policy Institute. Piles of books and papers fill shelves, cover his desk and migrate to any open floor space. He is clothed in his signature ­casual sportswear, down to the running shoes. For him, dressing up is adding a bow tie and jacket. “We’re beginning to see, not only in this country but elsewhere, thinking on a scale that we’ve never seen in energy before,” Brown says. “The challenge is not so much to find the energy—it’s there: solar and wind and geothermal. The challenge is how to harness it economically and get it to people who can use it.”

Brown still has work to do on other issues he has been hammering at for nearly half a century: to convince people that global food supplies could become catastrophically short and that population pressures are hastening the day when resources of all kinds begin to run out. Never modest in his pronouncements, he sees nothing short of a collapse of civilization if governments do not pay attention to disturbing overlapping planetary trends: plunging water tables, depleting and eroding soil, and dwindling grain stocks, with global warming in the background quickening the slide.

Although to supporters Brown has become something of an icon or touchstone, his most persistent critics have faulted him for decades of sounding (and skillfully publicizing) alarms on such threats, at least some of which never materialized in time frames he envisioned, costing him credibility. Former colleagues who credit him with being a wide-ranging visionary in the 1970s, at a time when “environmentalism was mostly about saving pandas,” as one described it, and remember him as a generous and encouraging mentor nonetheless often came to find him stubborn and inflexible in his convictions and often unwilling to gain from criticism.